Finned tube



Feb. 6, 1940.

E. G. LEHMAN FINNED TUBE Filed April 15, 1337 2 Sheets- Sheet 1 mm! mwwm (Ittomegs Feb. 6, 1940.-

E. e, LEHMAN FINNED TUBE Filed April 15, 1937 '2 sheets-sheave Ewowb g 3m entor v (Ittornegs 25 tice of this invention,

Patented Feb. 6, 1940 PATENT OFFICE FINNED TUBE Edward G. Lehman, York, Pa., assignor to York Ice Machinery Corporation, York, Pa., a corporation of Delaware Application April 15, 1937, Serial No. 137,102

5 Claims.

This invention relates to refrigeration, and more particularly toheat exchange units of the finned coil type.

One object of this invention is to provide a finned coil which may be assembled on the job from a single straight length of tube stock, and av section or sections cut from a length of fin stock, such fin stock including a plurality of fins secured in spaced relation to each other and Y 10 forming a unitary structure of any desired length.

Another object is to provide a finned coil which may be assembled as above indicated and wherein the fin section or sections are locked in place 16 upon their individual runs of the coiled tube by expanding the tube.

Another object is to provide a finned coil, the fins of which are so formed and connected together prior to their application as fins that accurate alignment and spacing thereof is assured before and after they are locked to the tube, and a substantially stifi' structure as a whole is finally produced.

An important advantage incident to the pracis that stock lengths of tubing, and stocklengths of fin assembly may be kept available at the point of use and there made up into complete units of various dimen sions in accordance with the requirements of the particular installation.

Other objects and advantages will become ap-' parent to those familiar with the art to which this invention relates'as the following specification is read in connection with the accompanying drawings, in which,

Fig. 1 is a perspective view of a portion of a fin section constructed in accordance with this invention. i

Fig. 2 is a perspective view of a header plate.

Fig. 3 is a longitudinal sectional view showing a portion of a length of tube with two fin sections and their header plates loosely mounted thereon and prior to the bending operation.

' Fig. 4 is atransverse sectional view on the 5 line '44 of Fig, 3, a portion of the header plate being broken away to expose a part of the fin structure. The clearance between the tube, and header plate and fins encircling the same, is

exaggerated in the drawings. Actually a sliding 50 fit is made between the elements.

Fig. 5 is a fragmentary sectional view showingthe edges of 'twofins and the means of securing the spacing ribbon strip to them.

' Fig. 6 is a side elevation of a completed unit.

Fig. 7 is a plan view thereof.

corners of the fin plates l2 and make a snug ing, may be adopted though that indicated has Fig. 8 is an end elevation of the same.

Fig. 9 is a view similar to Fig. 4, the tube having been expanded to bring it into intimate frictional or locked engagement with the fins and header plate.

Fig. 10 is a detail of a form of rivet used to secure the adjacent header plates to one another.

Referring to Fig. 1 of the drawings, the numeral l'l indicates a group of fin plates constructed and assembled in accordance with this invention. Each fin l2 comprises a thin rectangular shaped plate stamped to include stiffening ribs l3, and apertures l4 formed centrally thereof. r

Any desired number of fins l2 are assembled in spaced relation by means of a plurality of metal ribbonstrips l5. Each of these strips I5 is crimped atv equidistant points throughout its length to form pockets I6 which receive the fit therewith. The parts are secured together by indenting or embossing, as is clearly shown at I! in Fig. 5 of the drawings. Other means for securing these parts together, such as solderbeen' found satisfactory and is preferred.

A unitary fin assembly is thus produced wherein the fins are accurately spaced and aligned and secured against casual displacement. It can be readily cut into sections of any desired length by simply severing the ribbon strips l5 at the proper point. Stock units may be made up of any desired length and cut to different lengths or different stock lengths may be provided.

Peripherally flanged header plates are associated with each group of fins l2 when the coil and the fins are assembled. Fig. 2 of the drawings shows such a header plate and by reference thereto it will be seen to comprise a rectangularly shaped plate l8 apertured at to the fin plates l2, and provided with a peripheral flange 2| also apertured as at 22,

For illustrative purposes in-Figs. '6 to 8, a coil having six straight runs or passes has been chosen. It is to be understood'however that coils I of any desired dimensions and number of passes may be made up by proper selection of the length of tube and the number of. fin sections per group and number of groups.

In practicing this invention a length of tube 60 23 is 'cut from the straight tube stock. From the fin stock, sections or groups of fin plates of the required length and number (six sections in the instant case) are cut and threaded upon the tube by passing the tube .through the aligned I.

I9, similarly 40 expanding operations.

2 openings H in the individual fins l2, see Fig. 3.

Header plates l8, one at each end of each group of fins I2, are included, the tube 23 passing through theapertures l9 formed therein. Both the header plates l8 and the fin plates l2 make a sliding fit with the tube 23. It is entirely practicable, and in some instances may be desirable, to finally position the fins and header plates at this point. This may be done by expanding the tube by any of the well known methods, such as hydrostatic pressure or, by simply forcing an expanding tool through the tube. The fin sections and their associated header plates are, bf course, spaced from one another to provide a. free section of pipe for the return bends of the coil, and are accurately located at their calculated positions prior to such expanding operation.

If it is elected to expand the tube by hydrostatic pressure prior to bending it, a support such as a jig or the like will be necessary to protect against over-expansion those portions of the tube forming the return bends. However, the preferred method is as follows:

The tube 23 having the fins I2 and header plates l8 properly spaced and positioned thereon is bent to form a coil of the prescribed dimensions. The fin sections l2 will now be parallel with each other and being loose upon their respective passes of the coil may be shifted longitudinally'thereof to effect any final adjustment necessary to accurately align .the various groups. Similarly, the

sustaining fin structure, said sections being applied to said tube by threading thereon; flanged header plates associated one with each end of each of said fin sections by being threaded upon said tube, said fin plates and said header plates being frictionally locked in position by deformation of said tube, the header plates for adjacent passes being aligned; and connections between such aligned adjacent header plates. I

2. The method of producing finned coils which comprises threading a plurality of units each made up of a plurality of centrally perforated fins and spacing means permanently attached to said fins and adapted to hold the fins in parallel spaced relation to one another, anda plurality of end plates, one end plate at each end of each of said units, upon a continuous length of tubing, said units being separated from each other to aiford unfinned intervals between units, bending the tubing in such unfinned intervals to produce parallel finned runs, connecting the end plates of adjacent runs with each other and then while the fins and end plates are maintained in properly spaced relation, expanding the tube to lock the fins and end plates in heat exchanging contact with the tube.

3. Aheat exchange-unit of the finned coil type comprising in combination a tubular core formed from a single straight length of tube, having imposed thereon groups of rectangular fin plates,

flanged header plates i8 are brought into juxtaposition with their adjacent flanges 2| contacting, and the perforations 22 therein being aligned. These header plates l8 are now secured to each other by means of rivets 24, see Figs. 8 and 10. As shown most clearly in Fig. 10, the rivet used comprises a head 25 and a hollow shank 26. The shank 26 is inserted through the aligned openings of the adjacent flanges 2| and then peened over as at 21.

With the various elements thus accurately positioned it remains only to bring the fins I2 and header plates l8 into frictional or locked engagement with the tube coil 23. This is effected by expanding the tube 23, utilizing hydrostatic pressure to bring about this result.

An important advantage of expanding the tube subsequent to bending it is that working of the metal at the return bends during their formation hardens or stiffens the metal sufliciently at these points to withstand the pressure incident to the This obviates the necessity of supporting these sections at such time and so simplifies this step in forming the completed coil.

The header plates act to extend the surface of the coil, and to that extent may be considered as fins or the equivalent thereof.

While the invention has been described in exact form and detail, no necessary limitation thereto is implied, variations or modifications within the scope of the appended claims being contemplated.

What is claimed is:

1. A heat exchange unit of the finned coil type which includes a coil having a plurality of parallel passes formed from a single tube; a group of fins for each pass of said coil, each of said fin groups being a unit composed of a plurality of fin plates connected to each other to form a unitary selfeach-of said groups being formed as a unitary self-sustaining structure, including continuous spacers formed of strips of sheet metal crimped upon the corners of successive fins; header plates one associated with each end of each group of fin plates, said groups of fin plates and said header plates being looked upon the tube by the deformation of the tube and said header plates being connected with each other independently of said groups of fin plates.

4. The method of producing a finned coil which comprises preparing at least two fin structure units, each unit comprising a plurality of onepiece fin plates, each fin plate having a tubereceiving aperture and the fin plates of respective units being permanently connected -with each other in spaced relation with their apertures aligned by a plurality of slender connecting elements, the connections being such that the unit is self-sustained and substantially rigid; inserting the tube into the aligned apertures of both units; bending the tubebetween such units to produce adjacent passes; and after such bending expanding the tube to lock the fins of the two units in place on the two passes thus formed.

5. That step in the process of fixing spaced apertured fins on a tube in which process the tube is inserted through the apertures in the series of fins and then permanently expanded to fix the fins in place, which step comprises permanently connecting the fins together by slender spacing means which form a part of the finished assembly and which offer no substantial resistance to airflow over the fins in any direction, such connection being made independently of the tube prior to the assembly of the fins with the tube and with sufilcient rigidity to maintain the spacing of the fins and their alignment during the expanding operation.

EDWARD G. LEHMAN. 

